1024-QAM High Image Rejection E-Band Sub-Harmonic IQ Modulator and Transmitter in 65-nm CMOS Process

An E-band high image-rejection sub-harmonic in-phase/quadrature (IQ) modulator for a high-order quadrature amplitude modulation (QAM) signal is designed and implemented on standard 65-nm CMOS technology. To maintain high image-rejection ratio of the IQ modulator over a wide bandwidth for high data-rate application, a load-insensitive analysis and a local oscillator (LO) broadband 45 degrees power splitter are proposed to achieve low amplitude and phase imbalanced structure. In addition, the doubly balanced sub-harmonic Gilbert-cell mixer with the advantages of good LO leakage suppression has been selected in the mixer design. The IQ modulator demonstrates a measured flat conversion gain of 0 +/- 1 dB from 55 to 85 GHz. The image rejection ratio is better than 40 dBc from 64 to 84 GHz. For millimeter-wave communication applications, the IQ modulator is integrated with a four-stage power amplifier to form a direct-conversion transmitter. The measured conversion gain of the transmitter is 33 dB and the measured saturated power is 11 dBm. Via high image rejection and good LO suppression of the modulator, a 1024-QAM modulated signal with a data rate of 500 Mb/s and 1.7% error vector magnitude is successfully demonstrated at 65 GHz.